The invention relates to an aerodynamic multiplewedge resilient bearing comprising two bearing halves which slide relative to each other as well as a resilient supporting and damping assembly which is secured to one bearing half and is formed of thin, elastic foils.
Aerodynamic bearings use air or other gases as a lubricant. The pressure in the lubrication clearance which provides the carrying capacity of the bearing is produced automatically, in much the same manner as in hydrodynamic bearings, by the sliding motion of the bearing surfaces in lubrication-clearance regions which converge in a wedgelike manner, and hence the name carrying wedge or lubrication wedge. A plurality of lubrication wedges over the circumference of the bearing will result in improved guiding and stability of the bearing.
The low viscosity of gases makes possible considerably higher sliding speeds than liquid-lubricated bearings will allow. At the same time the power dissipation in the bearing is reduced. Gases retain their lubricating properties over wide temperature ranges, from very low to very high temperatures. Moreover, with an aerodynamic bearing there are no sealing problems since it draws its lubricant from the working medium. This is why aerodynamic bearings can be used under extreme operating conditions, with extremely high circumferential speeds, and at both extremely low and extremely high operating temperatures. Applications include rapidly rotating shafts of any kind, such as in small gas turbines and exhaustgas turbosuperchargers and in other small turboengines.
In aerodynamic resilient bearings, one bearing half is provided with a resilient supporting and damping assembly consisting of thin elastic foils which form the bearing surface of this bearing half. This assembly yields to accommodate thermal expansion of the other bearing half so that an adequate lubrication-clearance height is maintained. The assembly also serves to dampen shaft vibrations which at specific critical speeds of rotation occur as resonant oscillations and, above a stability-limiting speed of rotation, as self-excited oscillations.
In a prior art radial bearing of this type, as disclosed in U.S. Pat. No. 3,747,997, the circular housing of the bearing is lined with a corrugated, pliant strip. Disposed thereon as the bearing surface is a straight, thin, pliant strip. This spring bearing is supported very softly and provided but little damping. Given the overall circular cross section of the bearing surface, this bearing does not constitute a multiplewedge bearing, and it is therefore able to transmit self-excited oscillations even at relatively low speeds of rotation.
Another known resilient bearing disclosed in British Patent Specification No. 1,447,651, uses a plurality of foils which at one end are fastened to the associated bearing half and whose other end overlaps the adjacent foil. The free ends of the foils in combination form the bearing surface. This bearing has better damping, however, the foils are elastically prestressed relative to the bearing surface of the other bearing half. This results in high starting friction and wear until the aerodynamic lubrication wedge is formed.